1. Field of the Invention
The present invention relates to a heat-sensitive printing machine for printing heat-sensitive paper or the like by the use of a printing plate formed with type, and, more particularly, to an improvement in the elastic members for elastically supporting the printing head of the heat-sensitive printing machine.
2. Description of the Prior Art
In recent years, a thermal printer has been used as a printing machine for printing the so-called "price labels", which are temporarily adhered in series to a web of backing paper and are printed with desired indicia such as the prices, production dates and/or bar codes of commodities before they are applied to the commodities. Another printing machine is also used, which is equipped with a heated printing plate formed with type bearing indicia such as the name and/or address of a shop together with a thermal head, without separately printing the aforementioned labels in advance with the the shop name and other information.
Moreover, the heat-sensitive printing machine is constructed such that a plate carriage carrying the printing plate and the heater is reciprocally moved to push the printing head against the labels, thereby effecting the heat-sensitive printing operations.
A printing plate of the type mentioned above cannot be made of an elastic material having a low heat resistance since it does not produce sufficient heat for the heat-sensitive printing operation. Rather, the printing slate must be made of a harder material such as metal. This is disadvantageous because the surfaces of the type fail to uniformly contact the surfaces of the labels if the parallelism between the label and type surface deteriorates due to any cause, such as an assembly error or wear. This results in a bad print in which the printed indicia are thin on one side.
Moreover, since the heat of the printing plate tends to be transferred by conduction from the aforementioned plate carriage to a reciprocal actuator for moving the plate carriage back and forth, there is another disadvantage in that the heat loss is uneconomically high. Still another disadvantage is that the printing plate cools down to a level lower than a proper printing temperature as a result of the heat loss, so that the print will tend to become faint or obscure.